Allow

{host:key.func(param)}

style macros in trigger description and then propagate it to Actions (via

{TRIGGER.DESCRIPTION}

).
It will allow user to send almost unlimited number of information in notification message (email etc.) about issue-related values.

{HOST.HOST} inside above macro should be allowed, to make it universal in Templates, i.e.:
{{HOST.HOST}

:key.func(param)}